In recent years, with advancement of digital technologies of electronic devices, there has been an increasing need for nonvolatile memory elements which are capable of preserving huge amount of data of images or moving pictures in a state where an electric power supply is in an off state. Patent document 1 and Non-patent document 1 disclose, in response to such a need, a technique in which the nonvolatile memory elements are formed using perovskite materials (e.g., Pr(1−x)CaxMnO3(PCMO), LaSrMnO3(LSMO), GdBaCoxOy (GBCO), etc) whose resistance values change according to electric pulses applied, state variable materials (hereinafter referred to as resistance variable materials) whose resistance values change are applied with predetermined electric pulses to increase or decrease the resistance values, and the resulting states having changed different plural resistance values are used to store numeric values, thus using the nonvolatile memory elements as multi-valued memory elements.
Patent document 1: U.S. Pat. No. 6,473,332 specification
Non-patent document 1: Tech. Dig.-Int. Electron Devices Meet. 2002, W. W. Zuang et al.